1. Field of the Invention
This patent application relates to sails and to sailboards, commonly known as windsurfers. More particularly the application relates to a device that rotatably connects a sail batten to a mast and provides tension and/or aerodynamic shape to a luff of the sail. Such a device is known in the art as a Camber inducer, or Cam.
In the following description the terms ‘Camber inducer’ and ‘Cam’ are interchangeable and refer to such a device that connects a batten and mast and provides tension and/or aerodynamic shape to the luff of a sail.
2. Background Information
Camber inducers (Cams) have been known for some time. Background concerning the need for Cams and their advent can be found in various patent publications including WO 08504377 A1; U.S. Pat. No. 4,686,921; U.S. Pat. No. 4,625,671; and U.S. Pat. No. 5,048,440.
A sail for a sailboard consists of a sail body having a leading edge or luff and a trailing edge or leach, and a luff pocket attached to the sail body by sewing its edges to the sail body at a location back from the leading edge so that a part of the sail body is located within the luff pocket. Battens are carried in chordwise batten pockets on the sail body between the luff and leach to stiffen and help shape the sail for improved aerodynamic efficiency. The battens are tensioned by batten tensioners located at the leach. The sail is mounted to the sailboard by a mast received within the luff pocket. Because the sail goes in both directions its aerodynamic shape must be able to rotate about the mast from a port tack to a starboard tack and visa versa. The battens are connected to the mast by Cams to help induce profile into the sail and set the entry shape of the sail and help control the aerodynamic foil shape.
Current Cams are of either a direct batten driven or sail body driven type. In the batten driven type the batten is received within a pocket between Cam halves at the back of the Cam. As the batten is tensioned it is pushed forward into Cam. This helps tension the luff pocket and gives very good aerodynamic shape to the sail. However, the leading edge of the sail body that lies within the luff pocket is not tensioned. This is a problem because the leading edge of the sail body carries part of the vertical load on the sail which helps maintain the aerodynamic shape of the sail between the battens.
The above problem is overcome by the sail body driven arrangement where the batten tip is captive at the leading edge of the sail body. This is achieved by a batten tip fitting which is attached (by sewing of otherwise) to the leading edge of the sail and located within the back pocket of the Cam. Compression of the batten tensions the sail body from the leading edge to the trailing edge, but does not drive the cam forward against the mast and so does not tension the luff pocket. Instead luff pocket tension is fixed by the dimension of the pocket, Cam and batten tip fitting. Luff pocket tension can be adjusted by shims fitted to the batten tip fitting allowing it to sit further into or out of the Cam pocket. This Cam arrangement tensions the leading edge of the sail body but rotation of the Cam is stiffer and the sail body snaps from one tack to the other more violently. Often the Cam will fail to rotate properly in the tack leaving the luff of the sail backed. The rider must hit or kick any stuck Cams to rotate them through the tack.
Accordingly, is an object of the present invention to provide a sail for a sailboard, and a device for rotatably connecting a batten to a mast and shaping a luff of a sail, which overcomes or substantially ameliorates the above problems.